My biggest problem is with the Pandaren race and culture being the theme for the next expansion. It would've been great if there was a zone with them, they were a neutral faction you get rep with or some instance... something small, like a content patch. The whole expansion centered around them I think is too much and also playing as one of 'em.
Besides that, I there are tons of stuff that interests me; the new talent system, the PvE challenges, the PvP focus (although we may just have been trolled on that one) and world bosses returning.
Grindhouse @ Laughing Skull (EU)
Current progress: 13/13 HC T11, 7/7 HC T12, 8/8 HC T13